Tic Tac Tot: Examining chemicals exposure in preschoolers

This is the fourth article of a five-part series about chemical exposure in pregnancy and childhood. For more context, start here.

 

Researchers from the Maternal-Infant Research on Environmental Chemicals (MIREC) team have looked at whether exposure to certain chemicals during pregnancy could have an impact on children’s early development.

 

MIREC is an ambitious, multi-year study of environmental chemicals and their possible health effects on mothers, starting during pregnancy and throughout childhood development, from infancy to adolescence.

In this study, researchers looked at neurodevelopment of 3 to 4 year old children through IQ tests. They also investigated whether chemical exposure could have an impact on the incidence of obesity in children. What they found is helping them develop links between chemical exposure and health later in life.

Cognitive abilities

Over the last few years, MIREC researchers have explored the potential impact of children’s exposure to chemicals and their cognitive abilities.

These include attention, memory, logic and reasoning, among others. They are usually measured through IQ tests. Other tests can provide information on the child’s neurodevelopment by examining autistic traits in children.

“The MIREC study isn’t representative of all children in Canada, since parents were able to determine whether or not they wanted to participate,” explains Dr. Bruce Lanphear, MD, MPHTM, Professor in the Faculty of Health Sciences at Simon Fraser University. “But it gives us some indication of the role of chemicals on childhood development.”

For example, researchers found that even a low exposure to lead and other chemicals could be linked to lower IQ scores.

Although the difference in IQ scores is usually between 1 and 5 points for each chemical, the cumulative impact of exposure to different chemicals can be substantial.

Researchers were also interested in finding out whether chemicals could be linked to autistic traits in young children. This doesn’t mean that the children would be diagnosed with Autism Spectrum Disorder, but that they perhaps exhibited traits, such as finding it hard to understand what others are thinking or feeling, getting anxious about social situations, or seeming uninterested in others.

During the course of their research, the MIREC team found that exposure to phthalates, a chemical used to make plastics, or lead could be linked to autistic behaviours. These traits were even more pronounced for children who had a higher exposure.

“Based on observational studies from various organizations, we are able to say there are no safe levels on children’s blood,” says Dr. Lanphear.

Researchers also found that lower folate during pregnancy was associated with increased autistic traits.

For children who had more autistic traits, higher phthalates, higher lead and lower folate increased the number of autistic traits, suggesting this is a more complex issue.

“It’s unlikely that a single chemical results in autism, but rather the cumulative exposure to various chemicals,” continues Dr. Lanphear. “The interplay between genes and environment also comes into play.”

Asthma

Researchers have found biomarkers in children that could predict their likelihood of developing asthma or allergies later in life.

Researchers have found biomarkers in children that could predict their likelihood of developing asthma or allergies later in life.

While completing her Ph.D. research, Dr. Jillian Ashley-Martin, Research Scientist and Co-Principal Investigator of MIREC, found clues, called biomarkers, in umbilical cord blood that could predict the likelihood of children developing asthma and allergies later in life.

If a mother knows their child could be more susceptible, it would be easier to control their environment to reduce symptoms.

Unsurprisingly, children whose mother had allergies or asthma had more of these biomarkers. But they also found that higher exposure to air pollution during pregnancy also increased the number of these biomarkers.

“This helps us make the case for reducing exposure in order to benefit children’s health,” says Dr. Ashley-Martin.

In the case of air pollution, intervention has to come from a much higher level, not necessarily from the mothers themselves. It may be a question of reducing levels of these chemicals in the community.

Research like this provides information to decision-makers and can help guide their actions to change the future.

Obesity

Researchers also looked at the incidence of childhood obesity with children aged between 2 and 5 years old. They took physical measurements, but also looked at exposure to metals (arsenic, cadmium, mercury, lead) and 22 different types of phthalates.

“Children grow quickly so it is challenging to use one set of BMI standards for boys and girls of different ages,” explains Dr. Ashley-Martin. “We standardize for age and sex and we look at environmental chemical exposure related to BMI. We also measure the parents’ BMI to control for the influence of genetics.”

Researchers observed that exposure to lead and BMI was different for boys and girls. With boys there was no link, but girls with higher lead levels had a lower BMI. The team is currently working to better understand the sex-specific differences, and determine how environmental chemicals affect boys and girls differently.

While there have been some promising results, researchers will need to determine whether the link between each chemical and obesity persists over time, all the way into adolescence and adulthood.


The MIREC research is a key part of the Chemicals Management Plan. This plan seeks to reduce the risks posed by chemicals to Canadians and their environment by assessing chemicals used in Canada and by taking action on chemicals found to be harmful to human health and/or the environment.

Stay tuned over the next few weeks for more articles about the MIREC studies throughout the different life stages of mothers and their children.

Up next: Looking the impacts of chemical exposure for teenagers.

Find out more:

Maternal-Infant Research on Environmental Chemicals (MIREC) Research Platform

MIREC Canada